The invention relates to improvements in torque transmitting assemblies in general, expecially to improvements in assemblies which can be used to transmit torque between the output element of the engine and the input element of the change-speed transmission in a motor vehicle. More particularly, the invention relates to improvements in apparatus for damping angular movements of at least two coaxial flywheels relative to each other.
U.S. Pat. No. 4,274,524 to Nakane discloses a rotational torque transmission mechanism wherein a slip clutch is installed in series with a damper having a set of coil springs and a friction generating device acting in parallel with the springs. Torque which can be transmitted by the slip clutch is constant and exceeds the maximum nominal torque generated by the internal combustion engine which drives one of the flywheels. Consequently, the slip clutch yields and permits the two flywheels to turn relative to each other only when the torque which is transmitted by the engine fluctuates within a very wide range. While the patented mechanism is capable of reducing the strain upon the power train between the engine and the wheels of the motor vehicle, of contributing to the comfort of the occupant or occupants of the vehicle, and of reducing some noise, it fails to operate satisfactorily within the entire RPM range of the engine. One of the reasons is that, as mentioned above, torque which the slip clutch of the patented mechanism can transmit must considerably exceed the nominal torque which is transmitted by the engine. The patented mechanism is designed to account for tolerances in the manufacture of component parts as well as for the fact that torque which is to be transmitted is likely to vary as a result of wear and/or other parameters which change in actual use of the mechanism. Another drawback of the patented mechanism is that it transmits a substantial torque even if the engine is operated at a relatively low RPM, i.e., when the engine does not transmit a maximum torque. Consequently, the mechanism cannot filter out minor fluctuations and/or other variations of torque which is transmitted while the engine is operated at a relatively low RPM.